Mobile communication system, mobile station, switching station, and location registration method for mobile station

ABSTRACT

A decrease is realized in network load caused by a change in selection of location registration device or an increase or decrease in the number of installations, on a circuit switching network side. A mobile communication system includes a mobile station, a packet switching station, and a plurality of location registration devices that perform location management of the mobile station. With respect to the mobile station, after one location registration device is already selected from among the plurality of location registration devices, when the mobile station performs location registration, an NRI (Network Resource Identifier) included in a TMSI (Temporary Mobile Station Identifier) is transmitted to the packet switching station. The packet switching station makes a request for location registration with respect to the one location registration device, based on the NRI.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/684,458, filed Aug. 23, 2017; which is a divisional of U.S.application Ser. No. 14/171,308, filed Feb. 3, 2014; which is adivisional of U.S. application Ser. No. 13/824,895, filed Mar. 18, 2013;which is a National Stage Entry of PCT/JP2012/070421, filed Aug. 10,2012; which claims the benefit of priority from the prior Japanesepatent application No. 2011-176557 filed on Aug. 12, 2011; thedisclosures of all of which are incorporated herein in their entirety byreference thereto.

The present invention relates to a mobile communication system, a mobilestation, a switching station, and a location registration method for amobile station, and in particular to a mobile communication system, amobile station, a switching station, and a location registration methodfor a mobile station, in which are arranged a plurality of locationregistration devices that perform location management of a mobilestation on a circuit switching network side.

TECHNICAL FIELD Background

Non Patent Literature (NPL) 1 discloses a specification for a functionknown as CS (Circuit Switched) fallback that implements cooperationbetween LTE (Long Term Evolution) and a 3G circuit switching service.Furthermore, the article “4.3.2 MME” of page 11 of the same literaturediscloses that, in a case of a configuration of an MSC/VLR (MobileSwitching Center/Visited Location Register) pool where a plurality ofMSC/VLRs provide service with the same Location Area Identity, an MME(Mobility Management Entity) is to select a MSC/VLR by an IMSI Hashmethod of Non Patent Literature 2. It is to be noted that the IMSI Hashmethod is a method to obtain a hash by a modulo operation, with an IMSI(International Mobile-Station Subscription Identifier) that is anidentifier for uniquely identifying a subscriber within a network andthe number of MSC/VLRs inside a network as two keys.

Patent Literature (PTL) 1 discloses that when UE (User Equipment)initially accesses an SGSN (Serving GPRS Support Node) pool or the like,a RAN node such as an e-NodeB selects a suitable CN (Core Network) nodefor the UE in accordance with a NNSF (Non Access Stratum Node SelectionFunction) and a load splitting (distribution) rule. In addition, PatentLiterature 1 discloses that a RAN node finds and selects a CN (CoreNetwork) node where the UE is originally registered, by using an NRI(Network Resource Identifier) inside a TMSI (Temporary Mobile StationIdentifier) included in an initial direct forwarding message received bythe UE. That is, as long as the UE of Patent Literature 1 moves within apool, the CN node does not change.

Patent Literature 2 discloses an MME in which, for the MME where atracking area update request (TAU request) from a UE is converted to alocation area update request (LAU request), a location area updateresponse (LAU response) including an NRI is received from an MSC and isconverted to a tracking area update response (TAU response) for the UE.

CITATION LIST Patent Literature

PTL 1:

Japanese Patent Kohyo Publication No. JP2010-537523A

PTL 2:

Japanese Patent Kohyo Publication No. JP2011-508496A

Non-Patent Literature

NPL 1:

3GPP TS 23.272 ver.10.4.0 “Circuit Switched (CS) fallback in EvolvedPacket System (EPS); Stage (Release 10)”, [searched on Jun. 20, 2011],Internet <http://www.3gpp. org/ftp/Specs/html-info/23272.htm>

NPL 2:

3GPP TS 23.236 ver.10.2.1 “Intra-domain connection of Radio AccessNetwork (RAN) nodes to multiple Core Network (CN) nodes (Release 10)”,[searched on Jun. 20, 2011], Internet<http://www.3gpp.org/ftp/Specs/html-info/23236.htm>

SUMMARY Technical Problem

The following analysis is given by the present invention. An IMSI Hashmethod described in Non Patent Literature 2 is used in a case where a UEmoves from a pre UE movement packet switching station (written below as“old packet switching station”) to another packet switching station(written below as “new packet switching station”), and the new packetswitching station selects a location registration device (MSC/VLR) thatcarries out location registration.

At this time, if a Location Area of a movement destination of the UE iswithin the range of the same location registration device pool (MSC/VLRpool), even if the IMSI Hash is used, the new packet switching stationcan select the same location registration device (MSC/VLR) as thelocation registration device (MSC/VLR) that was selected by the oldpacket switching station and which has completed location registration.In this way, by implementing location registration without movement ofthe location registration device (MSC/VLR), it is possible to realize adecrease in network load.

In particular, in a case where a packet switching station works togetherwith the location registration device (MSC/VLR) with a goal ofdelivering an SMS (Short Message Service), since the locationregistration devices (MSC/VLR) form a relatively large locationregistration device pool (MSC/VLR pool), an effect is realized in thatthe network load described above is decreased even more.

However, in a case where a failure occurs in a path between a locationregistration device (MSC/VLR) to be selected and the old switchingstation, the old packet switching station may select another locationregistration device (MSC/VLR) as shown in FIG. 12 (refer to S902 to S904in FIG. 12). Thereafter, when the UE moves to the new packet switchingstation and makes a Location Registration Request, the new packetswitching station selects the location registration device (MSC/VLR)using the IMSI Hash method (refer to S911 to S912 in FIG. 12). At thistime, since in the IMSI Hash method a hash is obtained by a modulooperation, with an IMSI and the number of MSC/VLRs as described above astwo keys, the new switching station selects the same locationregistration device (MSC/VLR) as in S902 in FIG. 12 (refer to S911 toS912 in FIG. 12). As a result, since a location registration device(MSC/VLR) which has not completed location registration is selected,unnecessary signal messages are exchanged within the network.

Moreover, as shown in FIG. 13, when the number of MSC/VLRs belonging toa location registration device pool (MSC/VLR pool) increases ordecreases, since the location registration device (MSC/VLR) selected bythe IMSI Hash changes, re-selection of the location registration device(MSC/VLR) is performed by most UEs for which location registration hasalready been done, resulting in congestion of the overall network.

It is to be noted that in Patent Literatures 1 and 2, there is clearlyno disclosure of a configuration of selecting a location registrationdevice configuring the location registration device pool as describedabove, and after the mobile station has moved, of selecting a locationregistration device which has completed location registration.

It is an object of the present invention to provide a mobilecommunication system, a mobile station, a switching station, and alocation registration method for a mobile station, by which it ispossible to curb the exchange of unnecessary signal messages and networkcongestion, caused by a change in selection of location registrationdevice or an increase or decrease in the number of installations, on acircuit switching network side of the abovementioned locationregistration devices (MSC/VLR).

Solution to Problem

According to a first aspect of the present invention there is provided amobile communication system, comprising: a mobile station, a packetswitching station, and a plurality of location registration devices thatperform location management of the mobile station, wherein: with respectto the mobile station, after one location registration device is alreadyselected from among the plurality of location registration devices, anNRI (Network Resource Identifier) included in a TMSI (Temporary MobileStation Identifier) is transmitted to the packet switching station whenthe mobile station performs location registration, and the packetswitching station makes a request for location registration with respectto the one location registration device, based on the NRI.

According to a second aspect of the present invention there is provideda mobile station, used in a mobile communication system comprising apacket switching station and a plurality of location registrationdevices that perform location management of the mobile station, wherein:with respect to the mobile station, after one location registrationdevice is already selected from among the plurality of locationregistration devices, an NRI (Network Resource Identifier) included in aTMSI (Temporary Mobile Station Identifier) is transmitted to the packetswitching station when location registration is performed on a packetnetwork side.

According to a third aspect of the present invention there is provided apacket switching station, used in a mobile communication systemcomprising a mobile station and a plurality of location registrationdevices that perform location management of the mobile station, wherein:with respect to the mobile station, after one location registrationdevice is already selected from among the plurality of locationregistration devices, a request for location registration is made to theone location registration device, based on an NRI (Network ResourceIdentifier) included in a TMSI (Temporary Mobile Station Identifier),received from the mobile station when location registration is performedon a packet network side by the mobile station.

According to a fourth aspect of the present invention there is provideda location registration device, included in a mobile communicationsystem comprising a mobile station, a packet switching station, and aplurality of location registration devices that perform locationmanagement of the mobile station, wherein: with respect to the mobilestation, after the location registration device is already selected fromamong the plurality of location registration devices, a LocationRegistration Request is received from the packet switching station,based on an NRI (Network Resource Identifier) included in a TMSI(Temporary Mobile Station Identifier), received when locationregistration is performed on a packet network side by the mobilestation. According to a fifth aspect of the present invention there isprovided a location registration method for a mobile station in a mobilecommunication system comprising the mobile station, a packet switchingstation, and a plurality of location registration devices that performlocation management of the mobile station, the method comprising: a stepof selecting one location registration device from among the pluralityof location registration devices, with respect to the mobile station; astep of transmitting an NRI (Network Resource Identifier) included in aTMSI (Temporary Mobile Station Identifier) to the packet switchingstation, when location registration is performed by the mobile station;a step of making a request by the packet switching station for locationregistration with respect to the one location registration device, basedon the NM; and a step in which the one location registration devicereceives a Location Registration Request from the packet switchingstation. This method is associated with particular machines referred toas a location registration device, a packet switching station, and amobile station, as described above.

Advantageous Effects of Invention

According to the present invention, it is possible to curb the exchangeof unnecessary signal messages and network congestion, caused by achange in selection of location registration device, or an increase ordecrease in the number of installations, on a circuit switching networkside.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram for describing a configuration of an exemplaryembodiment of the present invention.

FIG. 2 is a continuation diagram of FIG. 1.

FIG. 3 is a diagram for describing a configuration of a first exemplaryembodiment of the present invention.

FIG. 4 is a sequence diagram for describing operation of the firstexemplary embodiment of the present invention.

FIG. 5 is a diagram for describing a configuration of a second exemplaryembodiment of the present invention.

FIG. 6 is a sequence diagram for describing operation of the secondexemplary embodiment of the present invention.

FIG. 7 is a diagram for describing a configuration of a third exemplaryembodiment of the present invention.

FIG. 8 is a sequence diagram for describing operation of the thirdexemplary embodiment of the present invention.

FIG. 9 is a diagram for describing a configuration of a fourth exemplaryembodiment of the present invention.

FIG. 10 is a sequence diagram for describing operation of the fourthexemplary embodiment of the present invention.

FIG. 11 is a sequence diagram for describing operation of a fifthexemplary embodiment of the present invention.

FIG. 12 is a diagram for describing flow of location registrationprocessing according to methods of Non Patent Literatures 1 and 2.

FIG. 13 is a diagram for describing flow of location registrationprocessing according to methods of Non Patent Literatures 1 and 2.

MODES

First a description is given of an outline of an exemplary embodiment ofthe present invention, making reference to the drawings. It is to benoted that reference symbols in drawings attached to this outline areadded for convenience to respective elements, as an example in order toaid understanding, and are not intended to limit the invention to modesof the drawings shown.

The present invention, in an exemplary embodiment thereof as shown inFIG. 1, can be realized by a configuration including: a plurality oflocation registration devices 31 to 3 n that perform location managementof a mobile station on a circuit switching network side; a firstswitching station (a first packet switching station) 21 that, onreceiving a Location Registration Request from a UE (mobile station) 10,selects one location registration device from among the plurality oflocation registration devices 31 to 3 n in accordance with a prescribedrule and requests location registration; the UE (mobile station) 10; anda second switching station (a second packet switching station) 22 thatis located at a movement destination of the mobile station.

Specifically, the UE (mobile station) 10 receives a Location Responseincluding information 51 for identifying a location registration deviceselected by the first switching station (first packet switching station)21, from the first switching station (first packet switching station)21. As shown in FIG. 2, with movement from a service area of the firstswitching station (first packet switching station) 21 to a service areaof the second switching station (second packet switching station) 22,the UE (mobile station) 10 transmits a Location Registration Requestincluding information S2 for identifying a location registration deviceselected by the first switching station (first packet switching station)21 to the second switching station (second packet switching station) 22.The second switching station (second packet switching station) 22 makesa request for location registration to the location registration device31 for which the first packet switching station has performed locationregistration for the mobile station, based on the information S1included in the Location Registration Request.

As described above, according to the present invention, the secondswitching station (second packet switching station) 22 also performs aselection of a location registration device in which the first switchingstation (first packet switching station) 21 has actually performedlocation registration. Accordingly, it is possible to curb the exchangeof unnecessary signal messages and network congestion, caused by achange in selection of location registration device or an increase ordecrease in the number of installations, on a circuit switching networkside of the mobile station. It is to be noted that in a case where theinformation S2 included in the Location Registration Request indicatesthat the UE (mobile station) 10 is registered in a location registrationdevice other than the location registration devices 31 to 3 n (alocation registration device not belonging to the pool in question), thesecond switching station (second packet switching station) 22, similarto the first switching station (first packet switching station) 21,selects one location registration device from among the plurality oflocation registration devices 31 to 3 n, and requests locationregistration.

First Exemplary Embodiment

Next, detailed descriptions are given concerning first to fourthexemplary embodiments of the present invention using a NRI (NetworkResource Indicator) as information for identifying a locationregistration device, making reference to the drawings. FIG. 3 is adiagram that schematically represents a configuration of a firstexemplary embodiment of the present invention.

Referring to FIG. 3, a network configuration is shown that includes aplurality of MSC/VLRs 301 to 30 n that form a MSC/VLR pool forperforming location management of a UE (mobile station) 10 on a circuitswitching network side, and SGSNs 201 and 202 that perform movementmanagement or authentication processing of the UE 10 arranged on thecircuit switching network side. It is to be noted that in the example ofFIG. 3 various types of RAN node and various types of gateway that aredescribed in Patent Literature 1 are omitted. In the MSC/VLR pool, theplurality of MSC/VLRs are configured to provide a service for the sameLocation Area (LA).

On receiving a Location Registration Request from the UE 10, the SGSN201 (202) selects an MSC/VLR to perform location registration for the UE10, from the MSC/VLRs 301 to 30 n in accordance with a prescribed rulesuch as an IMSI Hash method of Non Patent Literature 2 or the like, andrequests location registration. The selected MSC/VLR transmits aLocation Response including a TMSI (Temporary Mobile Station Identifier)via the SGSN 201 (202) to the UE 10.

The TMSI includes an NRI distributed to an MSC/VLR. The NRI is aninformation item by which the MSC/VLR can be uniquely identified withinthe MSC/VLR pool.

By providing the NRI to the new SGSN 202 (201) when a request forlocation registration is made, the UE 10 makes the SGSN 202 (201) selecta MSC/VLR for which location registration is done. At this time, in acase where the MSC/VLR indicated by the NRI is an MSC/VLR within thesame MSC/VLR pool, since all the SGSNs hold a common configuration forselecting a MSC/VLR from the NRI, the SGSN 202 (201) restrains change ofthe MSC/VLR, and before moving, the UE 10 makes a request for locationregistration to the MSC/VLR for which location registration is done.

Next, a detailed description is given concerning operation of thepresent exemplary embodiment, making reference to the drawings. FIG. 4is a sequence diagram for describing operation of the first exemplaryembodiment of the present invention. It is to be noted that in thedescription below, SGSN 201 is referred to as “old SGSN” and SGSN 202 isreferred to as “new SGSN”.

Referring to FIG. 4, first, the UE 10 transmits a Location RegistrationRequest (Attach Request, Routing Area Update Request, or the like) tothe old SGSN (S001 in FIG. 4). The old SGSN that receives the LocationRegistration Request selects an MSC/VLR using the IMSI Hash method ofNon Patent Literature 2, and transmits a Location Registration Request(S002 in FIG. 4).

The MSC/VLR that receives the Location Registration Request carries outlocation registration of the UE 10, and in addition assigns a TMSIincluding an NRI corresponding to itself (S003 in FIG. 4). Furthermore,the MSC/VLR transmits a Location Response to the old SGSN (S004 in FIG.4).

The old SGSN holds the TMSI included in the Location Response or VLRName or VLR Number (S004-1 in FIG. 4). Thereafter, the old SGSNtransmits a Location Response (Attach Accept, Routing Area UpdateAccept, or the like) including the TMSI to the UE 10 (S005 in FIG. 4).

Thereafter, in a case where the UE 10 moves to under the control of anew SGSN, the UE 10 transmits the NRI included in the TMSI to the newSGSN, and makes a Location Registration Request (Attach Request, RoutingArea Update Request, or the like) (S011 in FIG. 4).

The new SGSN that receives the Location Registration Request transmitsthe Location Registration Request to an MSC/VLR corresponding to theNRI, requested by a TMSI included in the Location Registration Request(S012 in FIG. 4).

The MSC/VLR that receives the Location Registration Request performsonly updating of a Location Area since location registration has alreadybeen done for the UE 10, and responds with a Location Response (S015 inFIG. 4).

The new SGSN holds the TMSI included in the Location Response or the VLRName or the VLR Number (S015-1 in FIG. 4). The new SGSN responds with aLocation Response (Attach Accept, Routing Area Update Accept, or thelike) to the UE 10, based on a Location Response received from theMSC/VLR (S016 in FIG. 4).

As described above, according to the present exemplary embodiment, thenew SGSN 202 selects the MSC/VLR for which the old SGSN 201 hasperformed location registration. As a result, for example, it ispossible to perform location registration of the UE 10 to the sameMSC/VLR, without being affected if a failure occurs in a path betweenthe old SGSN 201 and the MSC/VLR initially selected by the old SGSN 201,or a change occurs in the number of MSC/VLRs. As a result, nounnecessary messages flow in the network and a decrease in network loadis realized.

Second Exemplary Embodiment

Next, a description is given concerning a second exemplary embodiment ofthe present invention, in which the new SGSN (SGSN 202) of the firstexemplary embodiment described above is replaced by an MME. FIG. 5 is adiagram schematically representing a configuration of the secondexemplary embodiment of the present invention. A point of differencefrom the first exemplary embodiment shown in FIG. 3 is that the SGSN 202is replaced by the MME 212.

The MME 212 is a switching station arranged on a packet switchingnetwork side, and performs movement management and authenticationprocessing of a UE 10 similar to the SGSN described above.

Next, a detailed description is given concerning operation of thepresent exemplary embodiment, making reference to the drawings. FIG. 6is a sequence diagram for describing operation of the second exemplaryembodiment of the present invention. It is to be noted that in thedescription below, SGSN 201 is referred to as “old SGSN” and MME 212 isreferred to as “new MME”.

Operation of the present exemplary embodiment is different in the pointthat the new SGSN of the first exemplary embodiment is replaced by thenew MME, and specifically the point that, in S011A of FIG. 6, the UE 10transmits a Location Registration Request (Attach Request, Tracking AreaUpdate Request, or the like) to the new MME, and in S016A of FIG. 6, thenew MME transmits a Location Response (Attach Accept, Tracking AreaUpdate Accept, or the like) to the UE 10. Basic operation is otherwisethe same as in the first exemplary embodiment, and a description isomitted.

As described above, the present invention can be applied to a case wherethe UE 10 moves from under the control of the old SGSN to under thecontrol of the MME, and the new MME can be made to make a LocationRegistration Request to a location registration device in which the oldSGSN has actually performed location registration.

Third Exemplary Embodiment

Next, a description is given concerning a third exemplary embodiment ofthe present invention, in which the old SGSN (SGSN 201) of the firstexemplary embodiment described above is replaced by an MME. FIG. 7 is adiagram schematically representing a configuration of the thirdexemplary embodiment of the present invention. A point of differencefrom the first exemplary embodiment shown in FIG. 3 is that the SGSN 201is replaced by the MME 211.

The MME 211 is a switching station arranged on a packet switchingnetwork side, and performs movement management and authenticationprocessing of a UE 10 similar to the SGSN described above.

Next, a detailed description is given concerning operation of thepresent exemplary embodiment, making reference to the drawings. FIG. 8is a sequence diagram for describing operation of the third exemplaryembodiment of the present invention. It is to be noted that in thedescription below, the MME 211 is referred to as “old MME” and SGSN 202is referred to as “new SGSN”.

Operation of the present exemplary embodiment is different in the pointthat the old SGSN of the first exemplary embodiment is replaced by theold MME, and specifically the point that, in S001A of FIG. 8, the UE 10transmits a Location Registration Request (Attach Request, Tracking AreaUpdate Request, or the like) to the old MME, and in S005A of FIG. 8, theold MME transmits a Location Response (Attach Accept, Tracking AreaUpdate Accept, or the like) to the UE 10. Basic operation is otherwisethe same as in the first exemplary embodiment, and a description isomitted.

As described above, the present invention can be applied to a case wherethe UE 10 moves from a state under the control of the old MME to underthe control of the SGSN, and the new SGSN can be made to make a LocationRegistration Request to a location registration device in which the oldMME has actually performed location registration.

Fourth Exemplary Embodiment

Next, a description is given concerning a fourth exemplary embodiment ofthe present invention, in which the old SGSN (SGSN 201) and the new SGSN(SGSN 202) of the first exemplary embodiment described above arereplaced by MMEs. FIG. 9 is a diagram schematically representing aconfiguration of the fourth exemplary embodiment of the presentinvention. A point of difference from the first exemplary embodimentshown in FIG. 3 is that the SGSNs 201 and 202 are replaced by the MMEs211 and 212.

The MMEs 211 and 212 are switching stations arranged on a packetswitching network side, and perform movement management andauthentication processing of a UE 10 similar to the SGSN describedabove.

Next, a detailed description is given concerning operation of thepresent exemplary embodiment, making reference to the drawings. FIG. 10is a sequence diagram for describing operation of the fourth exemplaryembodiment of the present invention. It is to be noted that in thefollowing description, the MME 211 is referred to as “old MME”, and theMME 212 is referred to as “new MME”.

Operation of the present exemplary embodiment is different in the pointthat the old SGSN and the new SGSN of the first exemplary embodiment arerespectively replaced by the old MME and the new MME, and specificallythe point that, in S001A and S011A of FIG. 10, the UE 10 transmits aLocation Registration Request (Attach Request, Tracking Area UpdateRequest, or the like) to the new and old MMEs, and in S005A and S016A ofFIG. 10, the new and old MMEs transmit a Location Response (AttachAccept, Tracking Area Update Accept, or the like) to the UE 10. Basicoperation is otherwise the same as in the first exemplary embodiment anda description is omitted.

As described above, the present invention can be applied to a case wherethe UE 10 moves from a state under the control of the old MME to underthe control of an MME, and the new MME can be made to make a LocationRegistration Request to a location registration device in which the oldMME has actually performed location registration.

Fifth Exemplary Embodiment

In the abovementioned first to fourth exemplary embodiments, informationidentifying an MSC/VLR in which location registration has been completedis transmitted to a new switching station via a UE 10, but it ispossible to also use a configuration in which an old switching stationtransmits information identifying an MSC/VLR in which locationregistration has been done directly to a new switching station.

Below, a description is given concerning a fifth exemplary embodiment ofthe present invention in which it is possible to select an MSC/VLR inwhich location registration has been done with respect to the UE 10 inquestion, without using an NRI from the UE 10. Since the presentinvention can be realized by a configuration similar to the first tofourth exemplary embodiments described above, the following descriptionis centered on points of difference in operation thereof. Furthermore,the following description relates to a configuration having an old MMEand a new MME as shown in FIG. 9.

FIG. 11 is a sequence diagram for describing operation of the fifthexemplary embodiment of the present invention. It is to be noted that inthe following description, an MME 211 is referred to as “old MME”, andan MME 212 is referred to as “new MME”.

Referring to FIG. 11, first, the UE 10 transmits a Location RegistrationRequest (Attach Request, Tracking Area Update Request, or the like) tothe old MME (S201 in FIG. 11). The old MME that has received theLocation Registration Request selects an MSC/VLR using the IMSI Hashmethod of Non Patent Literature 2 or the like, and transmits a LocationRegistration Request (S202 in FIG. 11).

The MSC/VLR that receives the Location Registration Request carries outlocation registration of the UE 10, and transmits a Location Response(S204 in FIG. 1). The old MME transmits a Location Response (AttachAccept, Tracking Area Update Accept, or the like) to the UE 10 (S205 inFIG. 11). It is to be noted that an NRI need not be included in theLocation Response here. Furthermore, the old MME holds a VLR Name or VLRNumber of a transmission source of the Location Response (S204-1 of FIG.11).

Thereafter, in a case where the UE 10 moves to under the control of thenew MME, the UE 10 transmits a Location Registration Request (AttachRequest, Tracking Area Update Request, or the like) to the new MME (S211in FIG. 11).

The new MME that receives the Location Registration Request, requestsforwarding of Context of the UE 10, with respect to the old MME(Identification Request, Context Request) (S212 in FIG. 11). In a caseof the present exemplary embodiment, a TMSI is not included in theLocation Registration Request transmitted in S211 of FIG. 11, butinformation identifying the UE 10 is included. The new MME uses theinformation identifying the UE 10 as information for identifying anMSC/VLR for which location registration has been done.

The old MME that receives a request to forward the Context transmits aforwarding response (Context Response) of the Context that includesTMSI, VLR Name, or VLR Number that are held (S213 in FIG. 11).

The new MME that receives a forwarding response of the Context (ContextResponse) transmits a Location Registration Request to an MSC/VLRidentified by the TMSI, VLR Name, or VLR Number included in theforwarding response of the Context (Context Response) (S214 of FIG. 11).

The MSC/VLR performs only updating of a Location Area, since locationregistration has already been done for the UE 10, and responds with aLocation Response (S215 in FIG. 11).

The new MME holds the VLR Name or VLR Number of a transmission source ofthe Location Response received from the MSC/VLR (S215-1 in FIG. 11). Inaddition, the new MME responds with a Location Response (Attach Accept,Tracking Area Update Accept, or the like) to the UE 10, based on aLocation Registration Response received from the MSC/VLR (S216 in FIG.11).

As described above, according to the present exemplary embodiment,location registration is performed to a location registration device inwhich the old MME 211 has actually performed location registration,without going via the UE 10. In the present exemplary embodiment also,for example, it is possible to perform location registration of the UE10 to the same MSC/VLR, without being affected if a failure occurs in apath between the old MME 211 and the MSC/VLR initially selected by theold MME 211, or a change occurs in the number of MSC/VLRs.

A description has been given above of respective exemplary embodimentsof the present invention, but the present invention is not limited tothe abovementioned exemplary embodiments, and it is possible to addfurther modifications, substitutions, and adjustments, within a scopethat does not depart from fundamental technological concepts of theinvention. For example, in the first to fourth exemplary embodimentsdescribed above, descriptions were given of using an NRI as informationfor identifying an MSC/VLR for which location registration was done, butit is also possible to use a VLR Name or VLR Number as described in theabovementioned fifth exemplary embodiment.

In the same way in the abovementioned fifth exemplary embodiment, it isalso possible to use an NRI as information for identifying an MSC/VLRfor which location registration was done.

Finally, a described is given of the invention as can be incorporatedinto the scope of the claims of the present invention.

<First Mode>

A mobile communication system including: a plurality of locationregistration devices that perform location management of a mobilestation on a circuit switching network side; a first packet switchingstation that, on receiving a Location Registration Request from a mobilestation, selects one location registration device from among theplurality of location registration devices in accordance with aprescribed rule and requests location registration; the mobile stationthat, on moving from under the control of the first packet switchingstation, transmits a Location Registration Request including informationfor identifying the location registration device selected by the firstpacket switching station; and a second packet switching station thatmakes a request for location registration to the location registrationdevice in which the first packet switching station has performedlocation registration for the mobile station, based on informationincluded in the Location Registration Request received from the mobilestation.

<Second Mode>

The mobile communication system according to the first mode, wherein:the first packet switching station notifies the mobile station of anetwork resource identifier of a location registration device thatperforms location registration, and the mobile station transmits aLocation Registration Request including the network resource identifierto the second packet switching station.

<Third Mode>

The mobile communication system according to the first mode, wherein:the first packet switching station stores a network resource identifierof a location registration device that performs location registration.

<Fourth Mode>

The mobile communication system according to the first mode, wherein:information for identifying the location registration device selected bythe first packet switching station is information for distinguishing themobile station; and the second packet switching station makes a queryconcerning a location registration device that performs locationregistration for a mobile station, which has received a LocationRegistration Request, with regard to the first packet switching station,and performs location registration for a location registration devicethat the first packet switching station has responded with.

<Fifth Mode>

The mobile communication system according to the fourth mode, wherein:the first packet switching station uses any of TMSI, VLR Name, or VLRNumber, in order to manage a location registration device that performslocation registration for a mobile station, which has received theLocation Registration Request.

<Sixth Mode>

The mobile communication system according to any of the first to fifthmodes, wherein: the plurality of location registration devices forms aMobile Switching Center/Visitor Location Registrar pool.

<Seventh Mode>

The mobile communication system according to any of the first to sixthmodes, wherein: the first and second packet switching stations areeither of a Serving GPRS Support Node or a Mobility Management Entity.

<Eighth Mode>

A mobile station that selects one location registration device fromamong a plurality of location registration devices in accordance with aprescribed rule, and on moving from under the control of a first packetswitching station that performs location registration for a mobilestation, transmits a Location Registration Request including informationfor identifying the location registration device selected by the firstpacket switching station.

<Ninth Mode>

A packet switching station, to which a mobile station is connected, thatmakes a request for location registration to a location registrationdevice that performs location registration for the mobile station, basedon information for identifying a location registration device includedin a Location Registration Request received from the mobile station.

<Tenth Mode>

A location registration method for a mobile station, including: a stepin which a first packet switching station, on receiving a LocationRegistration Request from a mobile station, selects one locationregistration device from among the plurality of location registrationdevices in accordance with a prescribed rule and requests locationregistration; a step in which the mobile station, on moving from underthe control of the first packet switching station, transmits a LocationRegistration Request including information for identifying the locationregistration device selected by the first packet switching station; anda step in which a second packet switching station makes a request forlocation registration to the location registration device in which thefirst packet switching station has performed location registration forthe mobile station, based on information included in the LocationRegistration Request received from the mobile station.

The respective disclosures of the Patent Literatures and Non PatentLiteratures described above are hereby incorporated by reference intothis specification. The exemplary embodiments may be changed andadjusted within the scope of the entire disclosure (including the scopeof the claims) of the present invention and based on fundamentaltechnological concepts thereof. Furthermore, a wide variety ofcombinations and selections of various disclosed elements (includingrespective elements of the respective claims, respective elements of therespective exemplary embodiments and examples, respective elements ofthe respective drawings, and the like) is possible within the scope ofthe claims of the present invention. That is, the present inventionclearly includes every type of transformation and modification that aperson skilled in the art can realize according to the entire disclosureincluding the scope of the claims and to technological concepts thereof.

REFERENCE SIGNS LIST

-   10 UE (mobile station)-   21 first switching station-   22 second switching station-   31 to 3 n location registration devices-   201, 202 SGSN-   211, 212MME-   301 to 30 n MSC/VLR

1. A first mobility management node comprising: a controller; and amemory operatively coupled with the controller, wherein the controlleris configured to: receive an attach request message from a mobileterminal upon a change of a mobility management node to the firstmobility management node from a second mobility management node, theattach request message including a temporary identifier of a circuitswitched (CS) domain for the mobile terminal, a network resourceidentifier (NRI) of the CS domain being included in the temporaryidentifier and identifying a location management node in the CS domain;select a location management node, from a plurality of locationmanagement nodes serving a current location area of the mobile terminal,based on the received temporary identifier including the NRI; and send arequest message for updating a location information of the mobileterminal to the selected location management node.
 2. The first mobilitymanagement node according to claim 1, wherein the first or the secondmobility management node is a Serving GPRS Support Node (SGSN) or aMobility Management Entity (MME).
 3. The first mobility management nodeaccording to claim 1, wherein the location management node is a MobileSwitching Center/Visited Location Register (MSC/VLR).
 4. The firstmobility management node according to claim 1, wherein the temporaryidentifier is a Temporary Mobile Station Identifier (TMSI).
 5. Alocation management node comprising: a controller configured to assign atemporary identifier of a circuit switched (CS) domain for a mobileterminal, the temporary identifier including a network resourceidentifier (NRI) of the CS domain, the NM identifying the locationmanagement node in the CS domain; a transmitter configured to send amessage including the temporary identifier to the mobile terminal via asecond mobility management node; and a receiver configured to receive arequest message for updating a location information of the mobileterminal from the mobile terminal via a first mobility management nodeupon a change of a mobility management node to the first mobilitymanagement node from the second mobility management node, the firstmobility management node selecting the location management node, from aplurality of location management nodes serving a current location areaof the mobile terminal, based on the temporary identifier including NRI.6. The location management node according to claim 5, wherein the firstor the second mobility management node is a Serving GPRS Support Node(SGSN) or a Mobility Management Entity (MME).
 7. The location managementnode according to claim 5, wherein the location management node is aMobile Switching Center/Visited Location Register (MSC/VLR).
 8. Thelocation management node according to claim 5, wherein the temporaryidentifier is a Temporary Mobile Station Identifier (TMSI).
 9. A mobileterminal comprising: a receiver configured to receive, from a secondmobility management node, a message including a temporary identifier ofa circuit switched (CS) domain for the mobile terminal, the temporaryidentifier including a network resource identifier (NRI) of the CSdomain, the NRI identifying a location management node in the CS domain;and a transmitter configured to send an attach request message forupdating a location information of the mobile terminal upon a change ofa mobility management node to a first mobility management node from thesecond mobility management node, the request message including thetemporary identifier including the NRI used for selecting the locationmanagement node from a plurality of location management nodes serving acurrent location area of the mobile terminal.
 10. The mobile terminalaccording to claim 9, wherein the first or the second mobilitymanagement node is a Serving GPRS Support Node (SGSN) or a MobilityManagement Entity (MME).
 11. The mobile terminal according to claim 9,wherein the location management node is a Mobile SwitchingCenter/Visited Location Register (MSC/VLR).
 12. The mobile terminalaccording to claim 9, wherein the temporary identifier is a TemporaryMobile Station Identifier (TMSI).
 13. A system comprising: a controller;and a memory operatively coupled with the controller, wherein thecontroller is configured to: assign a temporary identifier of a circuitswitched (CS) domain for a mobile terminal, the temporary identifierincluding a network resource identifier (NRI) of the CS domain, the NRIidentifying a location management node in the CS domain; send a messageincluding the temporary identifier to the mobile terminal via a secondmobility management node; receive, by a first mobility management node,an attach request message from the mobile terminal upon a change of amobility management node to the first mobility management node from asecond mobility management node, the attach request message includingthe temporary identifier including the NRI; select, by the firstmobility management node, the location management node, from a pluralityof location management nodes serving a current location area of themobile terminal, based on the temporary identifier including the NRI;and receive a request message for updating a location information of themobile terminal from the first mobility management node.
 14. The systemaccording to claim 13, wherein the first or the second mobilitymanagement node is a Serving GPRS Support Node (SGSN) or a MobilityManagement Entity (MME).
 15. The system according to claim 13, whereinthe location management node is a Mobile Switching Center/VisitedLocation Register (MSC/VLR).
 16. The system according to claim 13,wherein the temporary identifier is a Temporary Mobile StationIdentifier (TMSI).